Paper is normally produced by continuously running machines that, through the delivery of a stock of cellulose fibers and water distributed from head-boxes, generate a ply of cellulose material on a forming fabric. The ply is typically dried and wound in reels having a very large diameter (known in the industry as parent rolls). These reels are subsequently unwound and rewound about a core material to form logs having a smaller diameter. The logs are subsequently divided into rolls having dimensions that are equal to the dimension of the end product. Paper products such as rolls of bath tissue, kitchen towels, or other tissue paper products are normally manufactured with this process.
Generally, rewinding machines (or rewinders) are used to produce convolutely wound rolls or “logs” of web material wound about a core. Rewinders are used to convert the large parent rolls of paper into retail sized rolls and bathroom tissue and paper towels. These rewinding machines typically wind a predetermined length of web material about a tubular winding core normally made of cardboard. These rolls, or logs, are then each cut into a plurality of smaller-size rolls intended for commercial sale and consumer use. The tubular winding core section remains inside each convolutely wound roll of web material. In both cases the end product contains a tubular core made of material that is different from that forming the web material.
Rewinding machines are generally divided into two categories depending on the manner in which the winding movement is provided. A first type of rewinding machine, known as a central spindle rewinding machine (or center winder), provides a spindle supported on support elements disposed between a pair of side walls. The center winder receives a tubular winding core on which the roll or log is formed by means of rotation of the spindle which, for this purpose, is typically associated with a drive means. The winding movement of the web material about the core is provided centrally by the spindle.
A second type of rewinding machine, known as a surface rewinding machine (or surface winder), uses the rotational movement of the tubular core (on which the roll or log is formed) provided by peripheral members in the form of rollers or rotating cylinders and/or belts. The roll or log is kept in contact with the rollers or rotating cylinders and/or belts during log formation. Exemplary surface winders are disclosed in U.S. Pat. Nos. 3,630,462; 3,791,602; 4,541,583; 4,723,724; 4,828,195; 4,856,752; 4,909,452; 4,962,897; 5,104,155; 5,137,225; 5,226,611; 5,267,703; 5,285,979; 5,312,059; 5,368,252; 5,370,335; 5,402,960; 5,431,357; 5,505,405; 5,538,199; 5,542,622; 5,603,467; 5,769,352; 5,772,149; 5,779,180; 5,839,680; 5,845,867; 5,909,856; 5,979,818; 6,000,657; 6,056,229; 6,565,033; 6,595,458; 6,595,459; 6,648,266; 6,659,387; 6,698,681; 6,715,709; 6,729,572; 6,752,344; 6,752,345; and 6,866,220. Additionally, exemplary surface winders are discusses in International Publication Nos. 01/16008 A1; 02/055420 A1; 03/074398 A2; 99/02439; 99/42393; and EPO Patent Application No. 0514226 A1.
Generally, a surface winder is comprised of three principle winding rolls that perform the surface winding process. These rolls are known to those of skill in the art as the first winding roller (or upper winding roll (UWR)), the second winding roller (or lower winding roll (LWR)), and the third winding roller (or rider roll (RR)). These respective rolls are named due to where, or how, they contact a winding log. The UWR and LWR contact the winding log on the upper and lower portions respectively and the RR “rides” on the upper portion of the winding log as it increases in diameter as web material is wound thereabout. The core enters the surface winder and is typically adhesively attached to a web material to be wound thereabout in a region of compression disposed between the UWR and LWR. The winding log (core plus any web material convolutely wound thereabout) is initially rotated by the UWR in a region disposed between the UWR and a stationary core cradle. The winding log is then rotationally translated to a region disposed intermediate the rotating, but stationary, UWR and LWR (known as the winding nest region). The RR contacts the surface of the rotating winding log in the winding nest region and translates away from the UWR and LWR as web material continues to be convolutely wound about the winding log (core plus all web material convolutely wound thereabout).
In an exemplary surface wind system, a web material is convolutely wound about a paperboard core of 1.5″ to 1.7″ diameter and of a length that corresponds to the width of the tissue parent roll which comes from the paper machine, usually in width from 65″ to 155″.
However useful, current surface winders do have known limitations. As shown in FIG. 1, when a core is inserted into the region between the UWR and the cradle prior to insertion into the winding nest area, the core must undergo a transformation where the surface speed of the core must be accelerated from zero (i.e., has no surface speed at the point of entry) to the surface speed of the UWR (i.e., UWR running speed). In other words, the surface speed of the core is accelerated from zero to the surface speed of the UWR while disposed within the region between the cradle and the UWR. However, it has been observed that several mechanics-related principles in this region of a surface winder can act to impact motion of the core through this introductory region of the surface winder to retard this required surface speed acceleration.
First, the entry portion of the cradle positioned at a fixed point disposed orbitally about the UWR typically has a smooth surface. An exemplary entry point is shown in FIG. 2. The placement of a core having zero surface speed into the entry point of the winding cradle and the ensuing contact with the web material in contact with the UWR can (and generally will) cause the core to slip (i.e., not spin and laterally translate) against this initial portion of the winding cradle. This slippage is represented by the arrow labeled “S” in FIG. 3. This slippage is believed to cause the core to oblongly deform into an ellipsoid shape.
Second, the glue-laden core is targeted to contact the web material in contact with the UWR at a predetermined location by the requirements of the winding process. Typically the targeted contact location on the web material is disposed immediately adjacent a perforation between two separable sheets of web material. If this targeted attachment location changes, several unfavorable results can occur in the early stage formation of the convolutely wound material.
For example, if the web attachment point occurs at a point removed backwards from the region near the perforation (e.g., behind the perforation), any excess leading web material will ‘fold-back’ upon the core and overlap the region of actual attachment of the web material to the core. This causes a consumer undesirable and unattractively wound product.
If the web attachment point occurs at a point removed forwards from the region near the perforation (e.g., ahead of the perforation), the web material can fail to attach to the core. This can result in the deposition of the adhesive disposed upon the core material (e.g., the so-called core glue) upon the manufacturing equipment. Ultimately, this can result in a build-up of core glue upon the surfaces of the process equipment and result in a process shut-down. Not only will the web material need to be re-threaded though the converting equipment, but adhesive will also have to be manually removed from the surfaces of the rewinding equipment such as the winding cradle and UWR.
Thus, there is a clearly defined need to increase the acceleration of the core surface speed at the point of insertion of the core into the winding cradle to prevent the drawbacks observed by current surface winding equipment that meets current manufacturing financial and processing targets.